First Dopplergrams

First MDI Dopplergram.

This is the first Solar Dopplergram observed from space. It was made by MDI on 20 December 1995. Note that the images were taken before the instrument had been aligned, so that the solar image was not centered in the field; but for compression the telemetry data were cropped to a disc where the sun ought to have been. This explains the crescent of meaningless data in the lower left and the odd shape of the image.

First MDI Centered & Tuned MDI Dopplergram.

This frame is the first centered Dopplergram obtained with MDI. It was observed on 21 December 1995, shortly after the MDI protective door was opened. The large left-right variation is the signal from Solar rotation. The Sun rotates with a period near 27 days (the equator goes faster, the poles slower) which means the surface is moving at about 2km/s, or about 4500miles/hour. The "texture" is a combination of the motion from the sound waves that permeate the Sun and the large (Earth-size) convective cells called "super-granulation". The primary science of SOI will be accomplished by analysis of many months of such velocity maps, one observed each minute. This image is the raw Dopplergram as computed on-board MDI (but reduced for this image). The full 1024x1024 pixel resolution gif image is also available. Also, as a postscript file. This image was provided to NASA and ESA for the initial SOHO press release.

  SOHO SOI/MDI Results.

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Last Modified by Amara Graps, SOI, on 13 November 1996.